Introduction

Protrusio acetabuli is a central acetabular defect resulting from migration of femoral head medial to Kohler’s line (1). This results in medialization of the center of rotation (COR) of the hip. Primary Total Hip Replacement (THR) in such situations can be technically demanding due to associated significant medial and proximal migration of the center of the joint, deficient bone medially (2) and reduced bony support to the acetabular component peripherally.

Figure 1: Protrusio Acetabuli

Cemented total hip arthroplasty resulted in promoting bone lysis and implant loosening, however, uncemented total hip arthroplasty with impacted morselized autograft with a porous coated cementless acetabular component provided a biological solution to bone deficiency and long-term fixation in arthritic hips with protrusion.(3,4) Functional outcome of uncemented total hip arthroplasty was evaluated by Harris hip score pre & post operatively in the cases. (5)(6)

Classification:

Figure 2: Sotelo-Garza and Charnley Classification (5)

The aim of this study is to evaluate the functional and radiological outcome of using impacted morselized autograft with a porous coated cementless cup in cases of protrusio acetabuli of hip joint. (7)(8)

Active and active assisted range of motion exercises started within the first 24-48 hrs. Partial weight bearing with a walker was advised up to 3 months until bone grafts appeared to be incorporated in x-ray. Full weight bearing started at 3 months. Patients were advised not to squat, not to sit crossed legged and not cross the leg across midline. Patients were called upon at 6 weeks, 3 months, 6 months, and 12 months follow ups. At each visit functional outcome was taken according to Harris Hip score along with an X-ray pelvis with both hips.

Figure 4: Morsellised autograft

After neck osteotomy, acetabular floor prepared while avoiding penetration of a soft, deficient medial wall until a bleeding bony surface was obtained. Acetabular periphery reamed using large sized reamers initially.

Results

Maximum patients (10) were in the age group of 50-60 years, with a female predominance of 8 patients (53%), and 7 male patients (47%). 10 patients had unilateral involvement whereas 5 patients had bilateral involvement. The most common etiology was found to be Rheumatoid Arthritis (10) followed by Idiopathic (7) followed by Ankylosing Spondylitis (3). 4 had mild, 7 had moderate and 9 had severe grades of protrusio. The operation time ranged from 60 to 120 minutes (mean= 79.4 ±14 mins). The blood loss ranged from 200-400 ml (mean=262±36 ml).

Table 1: Comparative mean values of Harris hip score at pre op, 1 month, 3 months, 6 months and 1 year follow up

The mean preoperative Harris Hip Score was 48 which improved to 90 at the latest follow-up. 10 hips (50%) had excellent,8 hips (40%) had good, and 2 hips (10%) had fair results.

Discussion

Study by Mullaji et al suggested that the use of impacted morselized autograft in conjunction with porous coated cementless acetabular component restored hip biomechanics, after an intermediate duration follow up. 30 primary THR’s were conducted with a 4.2 year follow up which showed excellent outcome in 90% patients, fair in 7 % patients and poor in 3% patients.(9)

Study by Atanu et al showed that using only cement for acetabular reconstruction in protrusio acetabuli has had unacceptably high rates of recurrence, with components migrating into the acetabulum and occurrence of thermal necrosis of the thinned out medial wall due to heat polymerization of the cement. (10) These were some of the factors responsible for poor outcome.

Table 2: Comparison of results of different techniques used to treat acetabular protrusio with primary THR in literature published since 2000

Conclusion

We treated 20 cases of Protrusio Acetabuli of mild, moderate, and severe grades by Sotello-Garza and Charnley by uncemented total hip arthroplasty using morselized autograft. It helps in restoring biomechanics of hip joint and preventing recurrence of protrusio. We observed fair, good, and excellent functional outcomes in our patients.

There was no evidence of progression of protrusio or socket loosening in any of our cases. Osteolytic lesions were also not encountered in our study. All bone grafts united within 4-6 months after surgery and continuous trabecular bone that grew through the host bone and the bone graft was apparent. But a larger sample size and a longer follow up are required to ascertain this fact.