The scope of our research is the application of a new surgical treatment, 3D hip, for young dogs with hip dysplasia characterized by hip laxity. The 3D hip implant is a patient-specific 3D-printed titanium implant that is designed to extend the dorsal acetabular rim of the hip joint and leads to joint stability and resolution of hip pain. Hip dysplasia is a common orthopedic disease in young dogs that can be treated surgically by invasive techniques like pelvic osteotomy to hip replacement and femoral head and neck incision.
So there is a need for minimally invasive procedure like the 3D hip implant, which can be treated bilaterally with rapid recovery preserving the joint. The 3D hip is laser-printed with titanium powder using a direct metal printing machine. Printing is computer-guided by the CT scan of the dog's pelvis, ensuring sufficient dorsal acetabular rim extension for perfect fit placement, and reversing the hip laxity to immediate joint stability.
Accuracy of the 3D hip implant placement is evaluated during surgery using fluoroscopy, but it may be affected by changes of bone and joint between the day of CT scan and the day of surgery or the lead time. So a reduction in lead term to two weeks would be ideal. The modified surgical hip approach provides an adequate view of the dorsal acetabular rim of the hip joint for implant placement.
The 3D hip implant increases femoral head coverage, decreases laxity of the dysplastic hip joint, and shortens recovery time. Bilateral application in one operative session is the major benefit of the 3D hip procedure. To begin, hang the affected limb of an anesthetized dog placed in lateral recumbency.
Secure the dog using a vacuum bean bag positioner. Scrub the limb twice with 4%chlorhexidine gluconate solution, followed by spraying it with 70%ethanol twice. Place four surgical waterproof drapes around the surgical site.
Secure and cover the distal limb with a sterile waterproof sock. Then add a layer of sterile cohesive wrap for additional protection. Cover the exposed skin of the entire surgical area with an iodine impregnated drape.
To begin, identify the tip of the greater trochanter, the cranial border of the proximal femur, the iliac wing, and the ischiatic tuber on the anesthetized dog. Then draw a line to make a skin incision. Perform the Ortolani subluxation test to confirm hip subluxation before making an incision.
Incise the skin sharply with a surgical knife starting from the cranial dorsal iliac spine. Then turn ventrally along the cranial border of the proximal femur and stop distally to the greater trochanter. Make an incision through the subcutaneous fat down to the fascia.
Sharply separate and incise the superficial leaf of the fascia latae muscle along the cranial border of the biceps femoris muscle. Retract the biceps femoris muscle caudally. After identifying the fatty triangle, separate it with blunt tipped dissecting scissors and index finger to provide access to deeper layers.
Using a surgical knife, incise the intermuscular septum between the superficial gluteal muscle, the middle gluteal muscle, and the tensor fascia latae muscle. With a handheld retractor, separate and retract the superficial and middle gluteal muscles dorsally to expose the insertion of the deep gluteal muscle. Use blunt tipped dissecting scissors to undermine the deep gluteal muscle close to the greater trochanter.
Pre-place a stay suture on the deep gluteal tendon, approximately one to 1.5 centimeters proximal from its insertion on the greater trochanter. Using a surgical knife, perform a complete deep gluteal tenotomy close to the bone. Use blunt tipped dissection scissors to free the deep gluteal muscle from the underlying joint capsule.
Then with the help of the periosteal elevator and index finger, subperiosteally elevate the deep gluteal muscle from the ilium and retract it dorsally. Using a periosteal elevator, partially free the iliacus muscle from the caudoventral border of the iliac shaft, and identify the insertion of the rectus femoris muscle. Remove all remaining soft tissue from the exposed iliac shaft for accurate positioning of the 3D hip implant.
Scratch the periosteum to stimulate bone ingrowth for secondary implant fixation. Identify the articularis coxae muscle caudal to the rectus femoris muscle overlying the joint capsule. Check the 3D hip implant before positioning and check the locking mechanism of the drill guide on the implant.
Confirm a positive Ortolani subluxation test before implantation. Fit the 3D hip implant into the iliac shaft, ensuring the implant's flange hook under the ventral border of the exposed caudoventral iliac shaft, just cranial to the bony prominence. Check that the rim extension part of the implant overlays the cranial dorsal part of the hip joint capsule without capturing any deep gluteal muscle.
Verify the implant position by visualizing and probing for optimal bone contact in all four exposed screw holes. Then confirm the absence of space between the iliac flange and the caudoventral iliac shaft. Drill the hole for the first screw, then measure the screw length and temporarily fix the implant in the desired position with one titanium self-tapping locking screw.
After intraoperative fluoroscopy of the hip joints, ensure that the curvature of the rim extension part of the implant is congruent with the curvature of the femoral head and acetabular rim. Once correct positioning is confirmed, insert three titanium self-tapping locking screws in the remaining screw holes to fix the implant to the ileal shaft. Next, execute flexion, extension, and abduction movements of the hip joint to check for femoral head or neck impingement.
Perform the Ortolani subluxation test to confirm the reversal of hip laxity. Reattach the cut ends of the insertional tendon of the deep gluteal muscle using a locking loop suture pattern and one to two mattress synthetic absorbable monofilament sutures. Repair the gluteal fascia and tensor fascia latae in a simple interrupted pattern.
Close the subcutaneous tissue with an absorbable suture and skin with a non-absorbable suture in a simple interrupted pattern. To confirm the implant positioning and screw placement, perform postoperative imaging consisting of CT scan of the hips or hip orthogonal radiographs in lateral oblique, and ventrodorsal views.
