The Treatment of Femoral Head Deformity and Coxa Magna by the Ganz Femoral Head Reduction Osteotomy

The aspherical coxa magna femoral head can be made more spherical by intra-articular osteotomy. The Ganz technique of femoral head reduction osteotomy to reduce the size and restore the spherical shape of the femoral head has been performed in 20 patients over the past 5 years. A good or excellent functional and radiographic result was obtained in 14 of the 20. A fair result (decreased pain but no improvement in range of motion) occurred in 3, and a poor result (stiffness and pain) occurred in 3. The preliminary results of this technique are therefore very promising.

Perthes disease often results in a nonspherical femoral head (coxa plana) that is enlarged (coxa magna) compared with the normal side, with a short femoral neck (coxa breva) and a relatively high greater trochanter (coxa vara). The femoral head shape can vary from spherical to ellipsoid, to cylindrical, to saddle shaped. The acetabulum may also change in shape conforming to the enlarged, flattened femoral head or becoming more dysplastic in reaction to the subluxed femoral head. The femoral head cartilage may be well preserved or degenerated. Degeneration of the femoral head cartilage is usually greatest in relation to the rim of the acetabulum. The rim of the acetabulum acts as a high concentration stress line that leads to indentation of the softened femoral head, contributing to the collapse of the femoral head. The cartilage along this indented part of the femoral head may become permanently concave as part of a saddle shaped femoral head. The best-preserved cartilage of the femoral head is often the lateral third, because this part of the head is permanently outside of the joint and experiences little wear and tear and no weight-bearing forces. Similarly, the medial cartilage of the femoral head is often well preserved because of the containment by the round acetabulum. The better molded the two are to each other (congruity), the less wear and degeneration in the medial third of the femoral head.

The treatment of Perthes disease can be divided into 4 time frames: precollapse; collapsed but not ossified; collapsed and ossified; remodeled and degenerative. Treatment during precollapse includes modalities to prevent collapse and speed reossification (bisphosphonates, core decompression, and containment methods ). Treatment after collapse but before reossification aims at reduction of the subluxation, restoration of range of motion, and molding of the femoral head to the acetabulum (containment methods using casting and/or osteotomy and soft tissue releases, and hip joint distraction ). Treatment after the femoral head is collapsed and ossified is aimed at reducing femoroacetabular impingement and at eliminating secondary deformities such as fixed flexion and adduction of the hip joint (valgus osteotomy and femoral head reshaping ). Finally, once the femoral head and the acetabulum have remodeled fully, incongruity and femeroacetabular impingement leads to degenerative changes of the cartilage of the femoral head and acetabulum. Treatment during this phase ranges from femoral head reshaping, hip arthrodesis, pelvis support osteotomy, and prosthetic joint replacement.

The prognosis in Perthes disease is very strongly correlated with the final shape of the femoral head. The Stulberg classification of the femoral head is the most prognostic indicator of longevity of the femoral head. Although painful degenerative changes of the femoral head leading to the need for joint replacement are the final outcome of most Stulberg 4 and 5 hips, femeroacetabular impingement is a probably much earlier and more common problem with Perthes hips including Stulberg 2, 3, 4, and 5. Reshaping of the femoral head with cheilectomy has met with variable success. Long-term follow-up of cheilectomy done prior to the recent surgical dislocation approach shows good short-term improvement but no alteration in the degenerative natural history of the disease. The recent introduction of new methods to evaluate, understand, and treat the impingement of the misshapen femoral head has led to a renaissance of interest in the treatment of late Perthes disease. The older procedure of cheilectomy of the femoral head has been replaced by arthroscopic or open osteochondroplasty of the femoral head. The feared complication of avascular necrosis (AVN) of the femoral head has been reduced by the “safe surgical dislocation method” introduced by Reinhold Ganz. This approach has permitted more aggressive and extensive safe resection of the enlarged, impinging portions of the femoral head, with restoration of spherical congruity and movement of the hip joint.

In 2001 Ganz and colleagues developed a new solution to the misshapen femoral head of Perthes disease. Ganz recognized that the central third of the enlarged femoral head was the most damaged while the lateral third had the best preservation of cartilage, as already explained. He therefore resected the central third of the femoral head while preserving and mobilizing the vascular pedicle to the lateral third. The resection of the central third was also done in a way to preserve the vascular pedicle to the medial third of the femoral head. After resecting the lateral third he advanced it to the medial third. Essentially, he removed the central part of an ellipsoid and brought the two spherical hemispheric ends together to reform a sphere. He called this femoral head reduction osteotomy (FHRO). This intra-articular osteotomy of the femoral head was stabilized with internal fixation screws.

The author has been performing the intra-articular FHRO since February 2006. The purpose of this article is to report the results of the author’s first 20 patients to undergo this procedure.

Patients and methods

Between February 2006 and February 2010, 21 patients with misshapen femoral heads underwent intra-articular FHRO to reshape the femoral head. One of these patients suffered a femoral neck fracture in surgery, resulting in conversion to a total hip replacement. This patient was eliminated from the study, leaving 20 patients between 1 and 5 years since the osteotomy (mean 2.7 years). The etiology of the femoral head pathology was Perthes in 15, adolescent AVN in 3, and dysplasia in 2 ( Table 1 ). This study comprises a retrospective follow-up of the radiographs and clinical notes of this group of patients. Fourteen patients were treated for the right hip and 6 for the left hip. There were 8 males and 12 females. The average age at the time of the osteotomy was 14 years (range 10–23 years). Five patients were skeletally mature at the time of the osteotomy. In the rest the femoral head physis was still open on the treatment side in only one.

Table 1

Cases of patients with misshapen femoral heads who underwent intra-articular femoral head reduction osteotomy (February 2006 to February 2010)

Patient	Age (y)	Sex	Diagnosis	Bilateral	% Pre	% Other Pre	% Other Post	Year/Month	AVN	ROM Pre	ROM Post	Pain Post	Gait Post	Result	Pelvis Osteotomy	Follow-Up (y)	EF	Biplanar
1	12	F	Dysplasia	Yes	72	—	—	2006/4	—	—	More	—	Better	E	Yes	5	—	—
2	16	M	AVN	—	87	115	92	2006/7	—	—	More	—	Better	E	—	5	—	—
3	20	F	Perthes	Yes	81	—	—	2006/9	—	—	More	—	Better	E	Yes	4.5	—	—
4	14	M	Perthes	—	71	140	100	2008/4	—	—	More	—	Better	E	—	3	—	Yes
5	11	F	Perthes	—	84	125	95	2008/4	—	—	More	—	Better	E	—	4	Yes	—
6	11	M	Perthes	—	70	150	100	2007/10	—	—	More	—	Better	G	—	3.6		—
7	15	F	Perthes	—	88	118	92	2007/10	—	Stiff	Stiff	—	Better	P	—	3.4		—
8	10	M	Perthes	—	57	160	84	2008/3	—	Stiff	More	Yes	Better	G	—	3	Yes	—
9	21	M	Perthes	—	67	150	100	2008/9	—	Stiff	More	—	Better	G	—	2.5		Yes
10	23	F	AVN	—	83	118	91	2008/5	—	—	More	—	Better	E	—	3.1		—
11	13	F	Perthes	—	80	119	100	2008/2	—	—	More	—	Better	E	—	3		—
12	11	M	Perthes	Yes	77	—	—	2009/6	—	—	More	—	Better	G	—	2.9		—
13	11	M	Perthes	Yes	62	—	—	2009/6	AVN	—	More	—	Better	P	Yes	2	Yes	Yes
14	11	F	Perthes	—	70	141	100	2009/9	—	—	Stiff	Yes	Better	P	Yes	1.5	Yes	—
15	13	M	Perthes	—	72	120	100	2010/4	—	Stiff	More	Yes	Better	G	—	1		—
16	17	M	Dysplasia	—	67	127	100	2010/11	—	Stiff	More	—	Better	G	Yes	1	Yes	Yes
17	13	M	Perthes	—	81	150	91	2008/9	—	—	Stiff	—	Better	G	—	2.5		—
18	13	M	Perthes	—	76	129	93	2008/9	—	Stiff	Stiff	—	Better	G	—	2.5		—
19	18	F	AVN	—	76	132	100	2009/10	—	Stiff	More	—	Better	G	—	1.5		—
20	12	M	Perthes	—	82	140	100	2009/10	—	—	Stiff	—	Better	G	—	1.5		—
Mean	14	—	—	—	75	133	96	—	—	Stiff	—	—	—	—	—	2.7	—	—