Knee arthrodesis with the Sheffield external ring fixator: Fusion in 6 of 10 consecutive patients

Figures & data

Table 1.  Patients

Case no.	Age	Sex	Primary diagnosis	No. of years from primary TKA to arthrodesis	Significant systemic diseases
1	55	F	OA ^a	3	Breast cancer, hypertension, sclerodermia
2	68	M	OA	8	Bronchitis
3	66	F	OA ^b	0.6
4	81	M	OA	4	Heart insufficiency, pulmonary embolism
5	70	F	OA	10	Addisons disease, asthma, pacemaker due to bradycardia
6	61	M	OA	13	Liver-transplanted, immunosuppressive drugs
7	66	M	OA	10	Prostate cancer, bronchitis
8	71	M	OA	0.6
9	78	F	RA	0.6
10	76	F	OA	14	Diabetes mellitus, osteoporosis, aorta stenosis

asecondary to sclerodermia

bafter fracture

Figure 1. Anteroposterior radiograph showing trabecular fusion across the entire length of the arthrodesis.

Figure 2. The assembled Sheffield Ring Fixator.

Table 2.  Results

A	B	C	D	E	F	G	H	I
1	1 DG	3	4	4	7.5	+	6	7
2	1 DG	2	Loose (11 mo)	No fusion (11 mo)	3	+	7	11
3 a	1 SR	3	4.5	10	2	–	1	10
4	2 D, 1 DG	3.5	3.5	3.5	Yes	+	10	7
5	1 D, 1 DG	4	4	4	1.5	+	1	15.5
6	3 re-TKAs, 2S, 1DG	3.5	Loose (10 mo)	No fusion (9 mo)	6	–	1	8
7	1 DG	3	3	7	5	+	8	7
8	1 S, 1 DG	3.5	Loose (13 mo)	No fusion (13 mo)	?	+	1	10
9	1 SR, 1 DG	3	3	6	5	+	2	6
10	1 DG	3.5	Loose (18 mo)	No fusion (18 mo)	?	–	12	18

^a Case 3: removal of TKA and XF in one stage.

A Case no.

B Revisions prior to arthrodesis

  D – debridement

  DG – debridement with removal of TKA and instillation of gentamicin spacer

  S – synovectomy

  SR – synovectomy with removal of liner

C External fixation time (months)

D Time to clinical fusion (months)

E Time to radiographical fusion (months)

F Leg shortening measured by wedge height in the erect position with a horizontal plane through the superior iliac anterior spines.

G Pin tract infection

H Postoperative time to full weight bearing (days)

Follow-up period (months)

Table 3.  Results from perioperative biopsies during the first-stage operation

Case no.	Gram-positive bacteria	Gram-negative bacteria	PCR^a	Scintigraphy^b	Suspected route of infection
1 c	No growth	No growth	–	+	Hematogenous
2 c	No growth	No growth	–		Hematogenous
3	Coagulase-negative staphylococci,	No growth			Cicatricial defect
	Finegoldia magna				after patella fracture
4	Streptococcus mutans	No growth			Hematogenous
5	No growth	Enterococcus faecalis			Hematogenous
		Proteus sp.
6	Hemolytic streptococcus group G	No growth			Hematogenous
7	Staphylococcus aureus	No growth			Hematogenous
8	Staphylococcus aureus	No growth			Hematogenous
9 c	No growth	No growth	–	+	Hematogenous
10	Staphylococcus aureus	No growth			Hematogenous

^aPCR: polymerase chain reaction with broad-range bacterial primers and DNA sequencing.

^bScintigraphy: technetium-99m leukocyte scintigraphy.

^cBlood tests and clinical findings indicated deep infection in cases 1, 2 and 9.