Hip Preservation—Complications of Periacetabular Osteotomy

Introduction

Acetabular dysplasia is a major cause of hip pain and dysfunction in young patients. Moderate to severe dysplasia, when left untreated, is an established cause of arthritis requiring total hip arthroplasty (THA) at an early age. ^, Congenital malformation of the acetabulum and femoral head results in malalignment and increased joint reactive forces that disrupt the labrochondral junction and cartilage, which may eventually result in osteoarthritis. ^, Significant pain and disability can result from acetabular dysplasia prior to osteoarthritis; therefore, joint preservation techniques such as the Bernese periacetabular osteotomy (PAO) have been developed to better optimize femoral head coverage, reduce patient pain, and prevent secondary osteoarthritis. ^,

The Bernese PAO, developed by Ganz et al. in 1988, is a commonly utilized technique that involves the Smith-Petersen approach and multiple hexagonal cuts around the acetabulum (while leaving the posterior column of the pelvis intact) to reorient the acetabulum. ^, This technique preserves stability and allows for early patient mobility. Postoperative clinical outcomes indicate major pain reduction and improved function in both young and older patients.

The predominant indication for PAO is symptomatic acetabular dysplasia in an adolescent or young adult with a correctable deformity and preserved range of motion. More severe acetabular dysplasia has also been found to be successfully treated with PAO; therefore, dysplasia secondary to neuromuscular disorders and Legg-Calvé-Perthes disease are appropriate indications. ^, Other indications for PAO include acetabular retroversion and posttraumatic dysplasia. ^, Borderline dysplasia and instability patterns, commonly associated with increased versional/torsional abnormalities, can be treated with PAO and concomitant open techniques. However, some patients are managed with concurrent or closely staged hip arthroscopy to manage the intraarticular pathology. The optimal treatment strategy has not been determined for this patient population.

Hip arthritis is a relative contraindication to PAO, as increased Tönnis grade 2 or 3 has been found to be a predictor of failure. However, some patients have had improved outcomes, and it may represent a viable alternative to THA in very young patients. Other contraindications include incongruence on radiographs, as well as young patients at risk of damaging the triradiate cartilage. ^,

The complication rate of PAO ranges from 4% to 42% depending on the report and the particular complication. Complications are further classified as major or minor depending on severity and impact on the patient. Major complications of PAO include nonunion requiring surgery, heterotopic ossification requiring surgery, permanent lateral femoral cutaneous or major sensorimotor nerve damage, and deep infection. Minor complications include asymptomatic pubic nonunion, lateral femoral cutaneous nerve dysfunction/paresthesia, superficial infection, and asymptomatic heterotopic ossification. Some studies have found the incidence of minor complications to be as high as 95%, with surgeon learning curve commonly acknowledged as a cause. The Clavien-Dindo-Sink classification is a more objective complication schema commonly used with young hip surgery that has demonstrated high interrater and intrarater reliability for hip-preservation surgery. Given that PAO is a complex surgical procedure with a variable complication rate, more exploration of complications—and ways to prevent or mitigate complications—is warranted. The purpose of this chapter is to review the complications of PAO, including the preoperative and patient factors, intraoperative technical issues, and postoperative ramifications.

Preoperative Factors

Patient selection and surgeon experience are important factors for a successful PAO outcome. Preoperative factors for PAO complications include:

(1)
Surgeon Experience
(2)
Obesity
(3)
Patient Age
(4)
Smoking Status

Surgeon Experience

An inverse relationship between complication risk and surgeon experience is noted, with multiple studies indicating surgeon inexperience with PAO technique as a significant factor in complications. ^, ^, Various authors reported more complications in the first PAO procedures of their series, likely due to the technically challenging nature of the surgery. ^, Hussell et al. found that 85% of the technical complications occurred during the first 50 procedures, suggesting that an important learning curve is associated with PAO. However, in a more recent study, only 6% of patients who underwent PAO by a group of 10 surgeons with an average of 9 years (range, 1–37 years) of experience suffered a major complication, which demonstrates that surgeons with sufficient experience can perform PAO with a low complication risk profile. In an effort to investigate the impact of training on PAO complications, Novais et al. reported the complication rate from two young surgeons from their first 4 years of practice. They found that with case exposure greater than 40 PAOs and progressive surgical responsibility during contemporary structured fellowship training, two young surgeons were able to perform PAO with a low risk of complications. Due to the challenging nature of the surgery, orthopaedic residency training alone is not sufficient to perform PAO. Rather, exposure in fellowship, cadaver training, visiting high-volume hip centers, and/or attending specialty courses may be necessary to improve PAO success. A mentored introduction to PAO surgery, with surgeries performed in conjunction with a senior experienced surgeon, may further mitigate the learning curve.

Obesity

Obesity is associated with an increased risk of complications in patients undergoing PAO. ^, Novais et al. found that the odds of a complication after PAO in an obese pediatric patient were 10 times higher than that of a patient with a normal body mass index (BMI). Complications seen more frequently included superficial and deep infections and wound hematomas. In another study, the average probability of a patient developing a major complication was 22% for an obese patient compared with 3% for a nonobese patient. Postoperative radiographic acetabular correction was nonsignificant between obese and nonobese patients in both studies, indicating that PAO surgery is reliable in improving radiographic acetabular coverage of the femoral head in both populations. ^, Increased wound healing complications are likely due to both an increased soft-tissue pannus anteriorly in these patients and an incision located over the anterior flexion crease. Other reasons proposed for increased complications in obese patients include difficult retraction and exposure, particularly for the posterior column osteotomy due to extensive soft tissue in the abdomen and pelvis, challenging repositioning after osteotomy due to obscured intraoperative anatomic landmarks, and poor intraoperative radiographs due to soft-tissue shadowing. Proper patient optimization, including weight management strategies and nutritional counseling, remain important in the preoperative period prior to surgery.

Age

Proper patient selection regarding age for PAO surgery is important for successful outcomes. Increased age and Tönnis grade 2 or 3 are relative contraindications for PAO. Likely due to increased osteoarthritis, older age has been found to be associated with poor outcomes. The increased rehabilitation demands may also lessen the results in older populations. Steppacher et al. assessed 20-year follow-up of patients treated with PAO and found increased age and Tönnis grade at time of surgery to be independent predictors of poor outcomes. Failure was 100% in patients with Tönnis grade 3 and 87% with Tönnis grade 2. Advanced age has been found to be an independent risk factor for conversion to THA in other long-term follow-up studies on rotational acetabular osteotomies. Similarly, in a more recent study of long-term PAO survivorship, hips of patients over 25 years old at time of surgery were three times more likely to be symptomatic after surgery than hips of patients under 25 years old, indicating that increased age has a significant impact on quality of life and subsequent reoperation. Older age has also been shown to negatively impact bone healing and has also been found to be an independent predictor of nonunion in PAO. ^,

Smoking Status

Smoking negatively impacts bone healing, leading to delayed union and nonunion in orthopaedic surgeries. ^, Matsunaga et al. found that superior pubic osteotomy nonunion in patients undergoing curved pelvic osteotomy was 10.7 times higher in smokers compared with nonsmokers, indicating that smoking status is a significant factor in postoperative healing. They recommended guidance on smoking cessation preoperatively as necessary to decrease nonunion risk. Similarly, a case series of painful nonunions after triple pelvic osteotomies found the majority of the patients to be heavy smokers; the authors recommended advising patients that smoking preoperatively is a risk factor for nonunion. Smoking has a well-known negative impact on soft-tissue wound healing postoperatively; we recommend cessation of smoking at least 4 to 6 weeks preoperatively to minimize the complications.

Intraoperative Complications

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