The study was approved by our Hospital Research Ethics Committee. An existing database of patients treated for osteogenesis imperfecta was used to identify all individuals who had undergone surgery since the beginning of 1980 and who were presently at least eighteen years of age and had at least thirteen years of follow-up after the surgical treatment. Thirty-two patients were identified, none of whom was still undergoing follow-up by our pediatric orthopaedic service. Two of the thirty-two patients had died of causes unrelated to the intramedullary rod procedures, seven had been lost to follow-up, and one declined participation. The twenty-two remaining patients were contacted by mail or by e-mail and asked to complete a questionnaire, designed by the authors, that asked about issues related to the rod treatment that they had undergone. Clinical details including reoperations and complications were obtained from medical records, and radiographs were obtained from both our institution and our affiliated adult institution.
The United Kingdom version of the Short Form-36 (SF-36) questionnaire was used to assess generic health status16, and the results for the study cohort were compared directly with population-based normative data from the United Kingdom17 with use of the unpaired t test. A p value of <0.05 was considered significant.
We also designed a nonvalidated disease-specific questionnaire to assess symptoms related specifically to the previously or currently rodded bones, including the surrounding joints, as well as to other aspects of the musculoskeletal system. Details of other nonsurgical treatment were also requested. Mobility outside of the patient's home was categorized as primarily involving use of a wheelchair, use of walking aids, or independent mobility without aids. The data from the questionnaire were analyzed with use of the McNemar test, with a p value of <0.05 again being considered significant.
Source of Funding
There were no external sources of funding for this study.
Seven (32%) of the twenty-two patients reported no further fractures of the long bones treated with rods, nine (41%) had one or two fractures, and six (27%) had three or more fractures. All long bones demonstrated growth following rod implantation.
The twenty-two patients (thirteen women and nine men) had a mean age of 24.7 years (range, eighteen to thirty-six years; median, 23.5 years) at the time of the final follow-up. Sixty-six rods had been inserted as a primary procedure. According to the Sillence system18, the osteogenesis imperfecta was classified as Type I in seven patients, Type III in ten, and Type IV in five (Table I). According to the Shapiro system19, the osteogenesis imperfecta was classified as congenita type in twenty patients and as tarda type in two patients. The indication for surgery in all cases was recurrent long-bone fracture with or without associated deformity. All patients had sustained multiple (three to more than thirty) long-bone fractures prior to surgical treatment.
Four patients had been treated previously with nonelongating intramedullary rods at other centers, and these rods were revised to Sheffield rods. All other Sheffield rod insertions represented primary surgical procedures, and these were carried out as paired procedures (e.g., both tibiae or the ipsilateral femur and tibia) unless otherwise indicated on the basis of the patient age, complexity of the deformity, or presence of an acute fracture.
The mean age at the time of the initial rod insertion was seventy months (range, twenty-four to 160 months). The mean duration of follow-up, measured from the time of the initial procedure, was nineteen years (range, thirteen to twenty-nine years).
Implant Outcomes (Table II)
Twenty-three (35%) of the sixty-six original telescopic intramedullary rods were exchanged. The most common reason for rod exchange (ten rods, 15%) was patient growth leading to disengagement of the male and the female component. In most cases, this exchange was performed prior to disengagement to avoid the risk of fracture at the disengagement site. Four of the remaining thirteen exchanges were performed because bending of the rod resulted in a lower-limb fracture that would have prevented proper rod elongation. Excluding the rods that were exchanged because of growth, 20% required exchange, resulting in an implant survival rate of 80%.
Ten additional reoperations (involving 15% of the sites) that did not require rod exchange were performed. Nine of these reoperations were performed because of infection or rod migration, and one femur required a rotational osteotomy to treat rotational malunion of a corrective femoral osteotomy.
Five additional complications did not require surgery. Two tibiae and one femur had radiographic evidence of nonunion of a corrective osteotomy but were not treated surgically as there were no associated symptoms. One superficial wound infection was treated with antibiotics. No premature physeal arrest was seen in any patient, although a substantial limb-length discrepancy that did not require surgical treatment was identified in one Sillence Type-I patient treated with bilateral femoral rods. An apparent infection within the knee joint in one limb of this patient had been treated with surgical debridement (with retention of the rod), resulting in a limb-length discrepancy even though physeal arrest was not observed. No surgery involving a long bone was pending for any patient at the time of the final follow-up; one patient was awaiting surgery for basilar invagination.
Patient Outcomes
Preoperative mobility was generally poor; eighteen of the twenty-two patients were wheelchair-dependent and only four were able to walk without aids. The number of patients who were able to walk independently with or without the use of aids increased significantly (p = 0.0015) to fifteen at the time of the initial postoperative follow-up (Fig. 2). However, the development of walking in patients with osteogenesis imperfecta is often delayed and can follow different patterns, suggesting that some members of the study cohort could have developed the ability to walk independently even if they had not undergone the surgery20,21. The improvement in walking ability was maintained into adulthood (p = 0.0077). Although the number of individuals who were wheelchair-dependent increased again between the initial postoperative visit and adulthood, this increase was not significant (p = 0.5465) (Fig. 2).
Patients were asked specifically about pain and discomfort related to the lower-extremity joints through which the rods had been inserted into the long bones, as well as about symptoms related to other parts of the musculoskeletal system. Four (18%) of the twenty-two patients reported pain related to rods that were still in situ. One of these patients reported discomfort at the ankle where the rod was protruding anteriorly but declined surgical intervention. In addition, the hip or buttock area was commonly associated with pain or discomfort, despite the extra-articular approach to the trochanter that was used for femoral rod insertion. Eleven of the twenty-one patients who had femoral rods in situ or had previously had such rods (including three of the four previously mentioned patients with rod-related pain) reported symptoms in the hip or buttock area. Of the three patients with femoral rod-related pain, one reported that the pain in this area was associated with activity, and two reported constant pain in this area. Five patients reported an annoying clicking in this area and three patients reported discomfort in this area that may or may not have been related to the rods, and one reported that the T-piece of the rod at the trochanteric entry point was mobile and discomfort occurred when this intermittently became jammed and required external pressure to relocate it. Only one patient reported stiffness of the knee, and no patient reported stiffness of the ankle, although five patients reported instability of the knee or ankle. Two patients reported knee pain, which was associated with a patellar fracture in one patient and with a knee infection that required removal of the femoral rod in the other patient. The latter patient was the one who reported knee stiffness. No decrease in joint space, osteophyte formation, subchondral sclerosis, or metaphyseal cysts were noted on any postoperative radiograph.
Fifteen (68%) of the twenty-two patients reported substantial back pain. The patients’ reports indicated that this was the most common symptom and that this area was a major cause of both pain and difficulty with activities of daily living.
Bisphosphonates had been administered in thirteen (59%) of the twenty-two patients, and eight of these patients believed that the bisphosphonates had been beneficial, primarily by decreasing bone pain rather than by preventing fractures. The bisphosphonate treatment in each of these patients was started after insertion of the intramedullary rods and at a much older age than is currently accepted as the standard at our institution.
When asked whether they were satisfied with the outcome of the surgery, all patients responded positively. When asked whether they would recommend this treatment to the family of a child with osteogenesis imperfecta, twenty-one of the twenty-two patients answered “yes,” and the remaining patient answered “unsure” because of a belief that treatment decisions should be made by a doctor and not by a former patient. Despite the intramedullary rod treatment, the mean subscores for all eight domains of the SF-36 were worse in the study cohort of patients with osteogenesis imperfecta than in the United Kingdom adult population as a whole. The difference was statistically significant for the four physical domains, social functioning, and vitality but not for role limitations and mental health (Figs. 3 and 4).
The principal aims of elongating intramedullary rods for the treatment of osteogenesis imperfecta are to correct deformity with the concurrent use of osteotomies, to splint the pathologically weak bone, to reduce the incidence of fracture with associated pain, and to prevent further deformity. Since the description of osteotomy, realignment, and intramedullary rod fixation by Sofield and Millar9, telescopic intramedullary rods have been introduced with the additional aim of prolonging the survival of the implant during periods of growth. The number of fractures following initial instrumentation is reduced by the use of telescopic rods, leading to high patient satisfaction.
Complications and Revision Surgery
Problems and concerns associated with the treatment of osteogenesis imperfecta with intramedullary rods have included the method of anchoring of the ends of the rod and the effect of the surgical procedure on the long-bone physes and the joint through which the rod is inserted. The first intramedullary rodding procedure with an extensible nail was performed in 1962 by Bailey and Dubow22. Common complications with this type of device were reported to include loosening at the trochanter, migration of the T-piece, and refracture22,23. Other centers subsequently identified similar problems, although the reported complication rates have varied greatly24-27. The variations in the reported complication and revision rates may have resulted from variations in how complications and revisions were recorded, the small number of patients in some studies, variations in the distribution of osteogenesis imperfecta types in the study cohorts (which was not always stated clearly), and variations in the duration of follow-up (which was only short to medium-term in some studies). Nevertheless, it is clear that although the original Bailey-Dubow technique was more successful than techniques involving nonelongating rods at treating deformity and reducing fracture rates28-30, this success came at the price of a high number of complications.
The Sheffield modification of the Bailey-Dubow extensible rods aimed to reduce the substantial rate of loosening of the T-piece by creating a larger and fixed T-piece10. Insertion of such a fixed T-piece requires exposure of the associated joint, which has raised concerns among the treating surgeons—in particular, regarding possible long-term effects following arthrotomy of the knee to insert the rod into the articular cartilage of the tibia and femur or following extensive release of the medial soft-tissue structures of the ankle to insert the rod into the tibial plafond. However, there is no clear evidence to date that use of a fixed T-piece is detrimental to patients in the long term. Other techniques have also since been developed to avoid the need for arthrotomy of the knee and ankle. One such modification involves the use of a threaded device that screws into both the proximal and the distal epiphysis, and another modification of the Sheffield rod uses an interlocking pin distally31,32. However, long-term data for these devices are not yet available, and complication rates (including rod migration) are still high. Osteogenesis imperfecta results in ligamentous laxity and commonly produces joint instability, which suggests that stiffness should rarely be a problem following arthrotomy and soft-tissue release. The rarity of symptoms of pain in the ankle and knee of the patients in the present study, despite the fact that most of the cohort was able to walk in adulthood, suggests that concerns involving the insertion site of these rods are unfounded at this duration of follow-up.
Anchorage of the rods in the cartilage of the trochanteric apophysis does remain a problem despite the larger, fixed T-piece. One-half of the cohort (including one patient who did not have femoral rods) reported either minor or major symptoms in this region. The third most common reason for reoperation was proximal migration of a femoral rod, which likewise suggests that fixation in this area has not been addressed successfully by the Sheffield rod design (Fig. 5). However, it is important to note that the cohort in our study consisted of patients who had been treated shortly after the introduction of the device, and the proximal T-piece was originally left slightly proud under the hip abductors. Because of the prevalence of migration that we observed, we now fix the T-piece into the trochanteric apophysis, which has reduced but not eliminated this complication.
Patient Satisfaction and Functional Outcome
Although surgical management of osteogenesis imperfecta involves numerous interventions, all of the patients were satisfied with the results of the procedure. As has been noted in previous studies of the outcome of osteogenesis imperfecta in adulthood33, a high proportion of the study cohort was academically successful and employed despite the physical impairment.
The SF-36 results were compared directly with United Kingdom normative data from the Oxford Health Life Survey, since it has been suggested that comparison with values from within the same country is more accurate34. The scores for all four physical domains and for two of the four mental domains, vitality and social functioning, were significantly lower in the osteogenesis imperfecta cohort than in the normal population.
Summary
Compared with nonelongating rods, the Sheffield telescopic system was associated with relatively low complication rates. The main drawback of the technique was the proximal fixation of femoral rods. Insertion of the rods via arthrotomies at the ankle and knee was not associated with high morbidity or symptoms at an average of nineteen years of follow-up. Patient satisfaction with telescopic intramedullary rod treatment was high, and mobility and functional scores relative to a normal population were acceptable given the underlying diagnosis of osteogenesis imperfecta. Future improvements in the technique may involve modifying the structural and biomaterial properties of the rods themselves and modifying the technique used for proximal fixation of femoral intramedullary rods.