Conservative Hip Surgery Case Title: Bernese Periacetabular Osteotomy for Residual Acetabular Dysplasia

Demographics

1.  

   Age: 21 years Sex: Female BMI: 22

    

2. Relevant Past Medical History

    

   Principal pathologies: Hip dysplasia with lateral uncoverage and labral tear

   Previous surgical procedures: None Medication: NSAR and physical therapy Other: None

   History of presenting complaint: Groin and trochanteric pain on and after activity. Unsuccessful nonsurgical treatment over twenty four months

    

3. Clinical Examination

    

   Symptoms: Groin and trochanteric pain on activity

   Range of motion: Normal range of motion which is painful at the end of motion

   Specific tests: Positive impingement and apprehension tests

   Main disability: Pain

   Scoring if available: No preoperative scoring

   Neurovascular evaluation: Normal

    

4. Preoperative Radiological

   Assessment/Imaging (Figs. 1.2,

   1.3 and 1.4)

    

    

    

   Fig. 1.2 Pelvic AP radiograph with a decreased anterolateral coverage of the femoral head, mild lateralization of the femoral head, and broken Shenton line

    

    

    

    

   Fig. 1.4 Abduction view used to assess achievable congruency and congruity which is good in this case

    

    

    

    

    

   Fig. 1.3 False profile view demonstrating the insufficient anterior coverage

5. Preoperative Planning

    

   Diagnosis: Severe acetabular dysplasia with lateral migration of the femoral head and ruptured labrum (Figs. 1.2, 1.3, and 1.4).

   Possible treatment options: Femoral varus osteotomy, augmentation procedures (Chiari, shelf), reorientation procedures (innominate osteotomy (Salter), double innominate (Sutherland, Hopf), triple innominate (LeCoeur, Steel, Carlioz, Tönnis) spherical osteotomies (Eppright, Wagner, Nonomiya), Bernese periacetabular osteotomy (Ganz).

   Chosen treatment method: Bernese periacetabular osteotomy.

   Selection of implants if applicable and rational: 3.5 mm steel screws, 50–80 mm long [2] (removal of long titanium screws is extremely difficult!). Short 2 mm screws [14]. Eventually

   4.5 mm screws for the large pelvic bone. Pelvic recon plate for 3.5 mm screws kept in reserve when extreme correction with large gaps or poor bone quality is to be expected.

    

   Expected difficulties: (1) Penetration of the first ischial osteotomy maybe not deep enough which can impede the complete separation of the acetabular fragment after all osteotomy steps are completed. It can be the cause of a hinged correction with lateralization of the fragment and of limitation of versional correction. (2) Difficulties with the osteotomy of the pubis. (3) Difficulties with spatial correction of the acetabular fragment. (4) Prevention of nerve injuries during the procedure.

   Strategies to overcome difficulties: (1) The first ischial osteotomy has to be repeated, eventually under fluoroscopic control. (2) Loss of purchase of the Hohmann retractor spiked medial to the osteotomy in the pubic bone will lead to a reduced visual control of this osteotomy. It may happen when the bone bridge between the osteotomy and retractor is too small leading to fissure lines and avulsion of the spike. (3) Resetting of the acetabular fragment and renewed radiographic control is necessary until the optimal position of the fragment is achieved. (4) Strict observance of details of surgical steps is imperative. Nerve lesions are not only the result of osteotomy; it can also be related to positioning of retractors and to the maneuvers for positioning of the fragment.

   Templating: A preoperative radiography of the pelvis with the leg of the involved hip in abduction (without external rotation) gives sufficient information about amount and directions of the three-dimensional acetabular correction. To specify acetabular version, the pelvis radiography must show the tip of the coccyx pointing to the symphysis with a distance of 1–2 cm from its upper border.

    

6. Surgical Note

    

   Patient’s position: Supine decubitus on an image table; the iliac spines should be leveled before draping in order to get orthograde intraoperative radiographs of the pelvis.

   Type of anesthesia: Conductive or general anesthesia.

   Surgical approach: [14]

   Main steps: A sequence of five osteotomies has to be performed. The space between the inferior capsule and psoas tendon is opened with scissors with spreading movements. Deep in this gap, the scissors should be kept proximal to the obturator externus muscle which is ensured by advancing the tip strictly in contact with the capsule. The tip of the closed scissors is used to feel the ischium. It is triangular in shape with the base posterior. Medially one should feel the tip of the scissors fall into the obturator foramen, and laterally the hamstring insertion protects the scissors from falling off the edge of the ischial bone. The space should be kept open to allow a curved bifid osteotome be placed onto the ischium. Proximally the subcotyloid groove should be felt with the osteotome which indicates the inferior border of the acetabulum. Start the first osteotomy at the tip of the triangle. Aim the osteotome toward the patient’s opposite shoulder. Then the lateral part of the osteotomy should complete the osteotomy. Some abduction and extension of the hip and flexion of the knee is mandatory, especially when the osteotome is placed over the lateral border of the ischium in order to relax and bring the sciatic nerve more laterally; extension of the hip is the most effective move. Begin the osteotomy with steady blows onto the osteotome, and the sur-geon’s hand should be brought more perpendicular to the patient’s body. Here it is important to listen to the change in sound and the feel of the bone. A solid sound indicates that the osteotome is in the bone. By side wiggling, feel that the osteotome is fully in the bone or exiting lateral or medial. Stop and slowly retrieve the osteotome palpating with the osteotome that the lateral aspect of the ischium is fully osteotomized. Commonly it is the lateral aspect of the ischium that still requires osteotomy. If so, translate carefully the osteotome laterally and repeat the osteotomy into the medial aspect of the ischium. Do not push the osteotome by hand; advancing the osteotome by careful hammer blows is safer. The ischial osteotomy is not a complete separation of the bone; it is sufficient with 2.5 cm of depth. It is more important to osteotomize the medial hard cortex. The lateral thinner cortex may eventually break at the end. The second oste-

    

   otomy is a complete separation of the pubic bone. To visualize the pubis medial to the iliopectineal eminence, the periosteum must be split and elevated superiorly and inferiorly allowing to pass blunt retractors around the bone in order to protect the obturator neurovascular bundle from being injured during the osteotomy. To prepare the transverse osteotomy, a small sliver has to be excised from the cis-cortex, just medial to the eminence. The osteotome has to be positioned in 45° with an inferomedial direction, away from the joint. Secure protection is guaranteed with the blunt retractors placed just where the osteotome exits the posterior cortex. Completion of the osteotomy is verified with levering moves of the osteotome. Optimal overall view is kept by replacing the Hohmann retractor in the pubis with a blunt retractor in the osteotomy gap. Before performing the third osteotomy, the inner surface of the quadrilateral plate is cleared from the thick periosteal cover to place a so-called reverse Hohmann retractor deep on the base of the ischial spine. The outer table is freed from musculature over a 3–4 cm distance between the anterior inferior spine and the upper border of the osteotomy of the superior spine. Using straight and curved periosteal elevators, this tunnel reaches into the greater sciatic notch and allows insertion of a second reverse Hohmann retractor. Both retractors protect the musculature from being injured with the saw blade during this supraacetabular osteotomy. The starting point, direction, and end point of the osteotomy should be marked out with an osteotome before positioning the saw blade. The starting point is the distal border or the middle of the osteotomy surface of the superior spine. The end point is the corner with the fourth, the retroacetabular osteotomy. This point is usually 1–1.5 cm anterior to the pelvic brim. It should give an optimal bony bridge between osteotomy and joint to allow firm grip of a 5 mm Schanz’ screw. When too close to the joint, the retroacetabular osteotomy may run into the joint; when too far, it may end in or fracture into the sciatic notch. An individual decision can be made safe with visual and palpatory control of the joint

   position relative to the planned osteotomy and with similar control of the direction of the retroacetabular osteotomy relative to the endpoint. The osteotomy is then performed with an oscillating saw under visual control on the inner side of the ileum. Care must be taken to finish the cut of the outer cortex at the same level as the inner endpoint. The fourth osteotomy is the retroacetabular continuation of the third osteotomy. Starting at the corner point at the inner side of the ilium, the first direction is given by the tip of the reverse retractor placed on the ischial spine. The correct placement is given by the fact that the retractor opens a wide gap. This would not be possible when placed more proximal or more distal, positions where the tip would fall into the greater or lesser sciatic notch; there it would not be able to produce a large space toward the quadrilateral plate. A 10-mm-straight osteotome is inserted into the corner point and directed toward the tip of the retractor. The palpating finger can give information whether this osteotomy direction leaves a 1–1.5 cm bone bridge posterior to the cut and whether it avoids penetration into the joint. When both questions can be affirmed, the osteotomy is performed. Only the inner cortex is cut which is secured by the edge of the osteotome staying visibly outside the bone. The osteotome should be advanced not more than 3–4 cm. At this moment, one may see a small step at the inner cortex of the third osteotomy. For the second part, a 15-mm-curved osteotome is used from medial to lateral to make the corner. It is advanced nearly perpendicular to the first osteotomy direction with the handle continuously pressed toward the patient’s abdomen in order to create a rather short distance to the outer cortex. Hammer blows become a metallic sound, when reaching the outer cortex. The step in the third osteotomy increases when the osteotome comes closer to the outer cortex. With further hammer blows and under soft tissue protection with the second reverse retractor, separation of the outer cortex will be completed. If needed, the separation of the outer cortex in the third osteotomy down to the corner point can be completed with a straight

    

   osteotome. Caudad osteotomy propagation of the outer cortex is not recommended. It would cut the periosteal blood supply from superior and inferior gluteal vessels to the acetabulum, which remain intact when the cortex is broken. Further mobilization of the acetabular fragment is made by levering the acetabular fragment with a large straight osteotome placed in the proximal part of the retroacetabular osteotomy. With a 5 mm Schanz’ screw inserted into the supraacetabular bone, the supraacetabular osteotomy gap can be opened to allow the placement of a large spreader for further widening of the gap. With this move, quite often the osteotomies propagate as an intentional fracture into the first, incomplete osteotomy of the ischium. In the majority of the cases, however, the fifth osteotomy has to be executed. It is a cut of the remaining bridge of the ischial bone. It is executed from medial to lateral under high tension produced by the spreader. A large bifid osteotome angulated 4 cm off the cutting edge, is placed against the posteroinferior border of the quadrilateral surface in such a way that the axilla is fitting to the pelvic brim. Opening of the handle to about 15–20° between the handle and quadrilateral surface allows to cut the bone posterior to the joint. Only the inner cortex must be cut. During this osteotomy, the hip should be somewhat extended and abducted, and at the same time, the knee should be flexed to allow relaxation of the sciatic nerve. After half way opening of the spreader, simultaneous and opposed rotation of Schanz’ screw and spreader will break the remaining lateral cortex and allow free spatial positioning of the acetabular fragment.

   Reconstruction techniques: Reorientation of

   the acetabular fragment has to be adjusted according to the individual deficiencies of femoral head coverage. Besides lateral deficiency of coverage as seen in most residual dysplasias after developmental dysplasia of the hip (DDH), there are hips with other deficiencies either isolated or in combination. Rather frequent are combinations with retroversion. Standard values of coverage do exist and most often reported is the CE angle in the frontal plane. However, deficiencies

   may not always be corrected to the normal value but rather to a balanced optimum of all values. In particular a normal CE angle should not be targeted when it is only attainable with a negative roof angle, a situation which is more critical in hips with a short roof. Schanz’ screw and spreader are the principal instruments for positioning of the acetabular fragment. For extreme and for reverse corrections, a second Schanz’ screw may be inserted into the supraacetabular bone from medial to lateral. Anterior rotation leads to an increase of anterior coverage, but at the same time, it increases lateral coverage. The achieved correction is preliminarily fixed with two or three K-wires. Intraoperative control radiography of the entire pelvis should be taken with neutral rotation and tilt of the pelvis. The following parameters are evaluated: The roof index should not be negative and is ideally 5–10°. Anterior and posterior border should meet at the lateral acetabular edge. The medial border of the femoral head should have the same distance to the ilioischial line as in the healthy opposite hip. If the opposite hip is also diseased, the distance should be 5–10 mm. Fluoroscopy is not as accurate as pelvic radiography. It is centered on the operated hip and not on the symphysis resulting in a different projection of the acetabular version; however, it may be used for repeated control when repositioning of the fragment was necessary. Before definitive fixation, joint mobility is checked. When internal rotation is clearly reduced, capsulotomy may reveal insufficient wasting of the anterior head-neck junction, leading to impingement after acetabular reorientation. This frequent finding can be addressed with osteochondroplasty. For definitive fixation, three 3.5 mm screws are used, two from the iliac crest into the fragment and one from the anteroinferior spine into the stable ilium near the sacroiliac joint. After capsular closure the rectus tendon is refixed with non-resorbable sutures, the fragment with the sartorius origin is refixed with one 2.0 mm screw, and further wound closure is performed layer by layer. Suction drainage is not necessary (Figs. 1.5 and 1.6).

    

7. Intraoperative Challenges

    

   Challenges and solutions: Challenge related to periacetabular osteotomy is coupled with experience but can also be associated with primary morphological particularities or residuals of previous surgery. At the beginning of a learning curve, every step is challenging; the first and the fifth osteotomy remain somewhat challenging, even for an experienced surgeon. It always necessitates special attentiveness and strict adherence to a surgical step sequence. Undersized and oversized pelves require adaptation of the feel for dimensions. This is even more delicate when confronted with extreme morphological particularities of bone and soft tissues; revision surgery can turn out to be extremely difficult presenting intraoperative scaring and findings, which could hardly be anticipated. Many surgical mistakes, small or big, with or without consequences have to do with a wrong interpretation of anatomic structures. This is why it is so important to get steadily acquainted by doing repeated cadaver dissections including simulation of the potential course of mistakes. Not infrequently, acetabular dysplasia is combined with a primary or secondary short neck and high-riding greater trochanter, eventually limiting abduction after the acetabular correction. Severe deformities will not even allow sufficient acetabular correction. Other hips have a patho-logically high or low version of the femoral neck. For both conditions, it is wise to address the femoral problem first with a relative lengthening of the femoral neck, advancement of the greater trochanter, and, where needed, a rotational osteotomy of the femur. The optimal level for such an osteotomy is the subtrochanteric area, where the necessary amount of correction can be established precisely with direct view on the proximal end of the femur. When starting the complex femoral and acetabular surgery on the femur, the first ischial cut of the periacetabular osteotomy can be executed via the femoral approach, allowing visual control and instrumental protection of the sciatic nerve.

   Unanticipated problems and solution: [2]

   Thorough description of decision making, including the reason for the final decision: Intraoperative complications which are detected only after surgery represent a particular challenge. For decision making, other factors like the age of the patient, the degree of the preexisting joint degeneration, and the expected result of revision surgery play an important role. The most frequent problem is acetabular retroversion either not addressed or increased with the correction. The consequence may be reduced internal rotation and anterior impacting impingement, while posterior subluxation or even dislocation is rare. Posterior instability can be clinically tested and often radiographically documented. When computer tomography confirms a posterior migration of the head, revision surgery is indicated. Re-intervention and correction of the version are easy when performed before consolidation of the osteotomies. After bone healing, a redo of the periacetabular osteotomy is more laborious than a primary procedure. When the head dislocates only in flexion, a posterior shelf osteoplasty may be sufficient. With the exception of severe retroversion, anterior impingement becomes typically symptomatic after a longer interval; the necessary evaluation should then include 3D simulation to understand better whether anterior osteochondroplasty may be sufficient or reorientation should be repeated. Persistent or newly developed lateral or anterior subluxation should be evaluated for an intra-articular obstacle, e.g., a femoral osteophyte; computer tomography gives the most relevant information. Such osteophytes are best removed with surgical dislocation. When functional views in abduction or flexion/abduction show good relocation of a subluxated head, it is obvious to redo an insufficient acetabular correction. Similar thoughts may be given to any other over-or under-correction. Additional femoral osteotomy is a rare alternative, mainly for undesired side effects. While intra-articular osteotomy cuts in the periphery of the acetabulum are often well tolerated, more central separations represent a

    

   substantial problem. Computer tomography is necessary to understand the pathomorphology of such a rare injury to the acetabulum and eventually the femoral head. When osteotomy or fracture gaps are relatively narrow without steps toward the head and when the head is not sublux-ating into a gap, one may wait and see in a patient late in his age spectrum for pelvic osteotomies; when the hip fails sooner or later, he may get a prosthesis. In a younger patient, it would be better to revise the hip by putting the acetabular fragment back into the preoperative position and perform a solid fixation. In some of these patients, a later approach for periacetabular osteotomy can be successful; others may not be prepared for a further trial. Surgical injury to nerves is a severe complication with a long healing period, and complete recovery may not be expected in every case. The incidence of sciatic and femoral injuries during periacetabular osteotomy among experienced surgeons is about 2%, the majority being sciatic lesions [15]. There is no evidence whether the use of fluoroscopy and/ or nerve monitoring can decrease the incidence. The surgeon should make a thorough analysis of the procedure to eventually define the move which most probably has produced the nerve injury. A computer tomography may give further information. It is necessary to document the early neurological deficiencies as accurate as possible. Electromyographic evaluation is more conclusive after three weeks from surgery. The patient has to be informed about the status, realistic expectations, and the progress of recupera-tion. A patient with a femoral nerve lesion may need a splint to stabilize the knee during walking, while a patient with a sciatic lesion should be supplied with a frame against a drop foot. Complete nerve sectioning is rare and if considered may be an indication for surgical revision together with a specialized surgeon. Other indication for revision may be a bone fragment which may have pierced the nerve. In the majority of nerve lesions, one keeps a wait-and-see attitude. Other therapeutic measures? Time of nerve recuperation?

8. Postoperative Radiographs

   (Figs. 1.5 and 1.6)

    

    

    

    

   Fig. 1.5 AP pelvic radiograph five years postoperatively with a well-centered femoral head sufficiently covered by the acetabulum and no signs of OA

    

    

    

    

   Fig. 1.6 Cross-table lateral radiograph demonstrating a well-recontoured femoral head-neck offset performed during the PAO procedure

    

9. Postoperative Management

    

   Chemoprophylaxis and anticoagulant treatment period: Perioperative antibiosis was given for 24 h. Until full weight bearing, prophylaxis for DVT was given.

   Gait/limb loading until full loading: Patients with a periacetabular osteotomy are young and can start with ambulation on elbow crutches at the second postoperative day. The amount of

    

   weight-bearing depends on the achieved stability of the fixation; this is normally about 15 kg, a value which the patient may test on a bathroom balance. To protect the refixation of the anterior superior spine, active lifting of the leg with extended knee should not be allowed until the first follow-up control at 6–8 weeks after surgery. At this time, an anteroposterior radiography is sufficient. When bridging callus at the pubis osteotomy and partial consolidation at the supraacetabular osteotomy becomes visible, loading of the hip can be increased stepwise, first with two crutches, going to one crutch in the opposite hand after two weeks. At this time, active raising of the extended leg is allowed as is full range of active motion. The patient is encouraged to do bicycling and swimming as well as exercises to reinforce the abductor musculature. Unrestricted loading is allowed 10–12 weeks after surgery provided a further radiography shows evidence of further consolidation. For walking free of crutches, the abductor musculature force should have reached an M5. Routine radiographs are performed at first year and every five years after surgery.

    

10. Follow-Up and Complications

     

    Report of postoperative complications and their management (i.e., recurrent dislocation): Postoperative hematoma is a rare complication with this surgery and may be provoked by a deficient coagulation system either preexisting or drug induced. Large hematomas are best treated with surgical evacuation, when the hematoma is located close to a major nerve, or when new and substantial bleeding from a vessel is suspected, emergency evacuation has to be executed, and the bleeding vessel is ligated. When a nerve is compressed and shows deficits, there is no time left for a diagnostic MRI or for preparing an embolization. Accidental overload or a fall in the postoperative period may have created a loss of correction. This has to be controlled with a radiography or even with a computer tomography. An eventual decision for revision surgery may be balanced under consideration of the aspects discussed above. Our patient had no postoperative or later complication.

    Scoring if available: The patient completely recovered. Since there has been no preoperative scoring, we did not ask her to fill a postoperative score.

     

11. Discussion

     

    Advantages of the applied method: In terms of corrective potential, the Tönnis and to a lesser degree the Carlioz osteotomy are comparable with the Bernese periacetabular osteotomy, while the soft tissue attachment in triples more distant to the acetabulum may interfere with larger corrections. The Bernese osteotomy is performed without the need for repositioning the patient during execution of the different cuts and allows large capsulotomy without extending the approach. All triples have a potential to narrow the birth canal, which is not the case with the Bernese osteotomy, an important aspect when considering that the majority of patients with acetabular dysplasia are young females; it may become critical for a normal delivery in the pelvis with bilateral correction. The retroacetabular cut of the Bernese osteotomy crosses the posterior part of the triradiate cartilage, reason why it should be reserved for older children and adults. In double osteotomies the inferior cut runs either through the joint or through the parasymphyseal bone, both versions have not found general acceptance. Spherical osteotomies are performed rather close to the joint, which may have a negative influence on the perfusion of the acetabular fragment; this is the reason why the authors caution against additional capsulotomy. Furthermore, when correction of version has to be supplemented, the advantage of large cancellous contact will get lost. Femoral varus osteotomies have been performed in the past mainly with the idea to stabilize the femoral head. Today, such correction is abandoned. However, it is more and more recognized that dysplasia can be complex and the femoral side may necessitate additional surgery. Most frequent procedure is anterior osteochondroplasty for insufficient head-neck wasting, followed by relative neck lengthening to reestablish a sufficient fem-oro-pelvic clearance. Not infrequently a varus

     

    osteotomy at the neck or intertrochanteric level has to be added including correction of version.

    Disadvantages of the method: The execution of the Bernese periacetabular osteotomy is rather demanding mainly because the ischial osteotomies have to be executed without direct visual control. Therefore, even experienced surgeons may prefer to do the cuts under fluoroscopic control, although there is no evidence that complications are less and precision of correction is higher. Alternative evidence-based techniques for the case: The best alternative would be the Tönnis

    osteotomy.

    Why is the chosen technique is better for this case? The general advantages are described above. However, the primary reason to choose the method is familiarity and experience with the technique.

    Indications and contraindications for your technique: For this patient, there is no contraindication of the chosen technique relative to others (see also under “Advantages of the Applied Method”). The variety of hip morphologies, the amount of preexisting joint degeneration, and the age of the patient, offer a range of indications from optimal to borderline. An ideal indication comes with a patient in his twenties with a round femoral head, well centered in the socket. The center-edge angle should be between 10 and 20°, and the joint space is large without narrowing in the abduction. Any subtraction in these parameters moves the indication gradually to borderline. In a 15-year-old, one may still formulate an indication when the head contour is irregular, and the osteoarthritis is grade 2, provided the head can be covered and stabilized under the socket. In retrospect, deferring a prosthesis for even less than 10 years would justify the indication. However, a similar condition in a 35-year-old may represent a contraindication.

    Learning curve and how to manage complica-

    tions: Periacetabular osteotomy is a demanding procedure which can hardly be learned from reading books or looking to videos. A good way to get familiar is a fellowship in a center with a high volume of such surgeries. Surgical experience with acetabular fractures is a good precondition. Cadaver dissections help to internalize what has

    been learned. Mentorship during the first surgeries is a good safeguard to avoid complications or to get advice about how to manage it.

    Level of evidence concerning the superiority of this method against others: The Bernese periacetabular osteotomy became a well-established method and is frequently used in Europe and North America. The reason may be a combination of its versatility as well as power and precision of correction. Several publications describe technique, complications, and up to 20 years of follow-up [2].